Water purification apparatus

ABSTRACT

Contaminated raw or waste water is delivered into at least one basin which is supported within a water-filled reservoir. The contaminated water in said basin is subjected to mechanical, biological and/or chemical purification, and the treated effluent is caused to overflow into the reservoir. The basin has a conical wall of supple nonporous material that yields readily to even slight movements of the water both internally and externally of the basin unit.

United States Patent Inventor Appl. No.

Filed Patented Assignee Priority Sten Jacquet Hagersten, Sweden 879,091

Nov. 24, 1969 Nov. 9, 1971 Sten Jaquet AB Hagersten, Sweden Dec. 2, 1968Sweden WATER PURIFICATION APPARATUS 3 Claims, 5 Drawing Figs.

U'.S.CI 210/123, 210/242, 2l0/256, 210/532 tlnt.Cl B0ld2l/02 Field ofSearch 210/83 [56] References Clted 1 UNITED STATES PATENTS l,ll8,6l4ll/l9l4 Allen 2l0/5l9X l,602,705 l0/l926 Riley et al.. 210/256 3,l84,065 5/ l 965 Bradford 2 l0/5 l9 3,385.786 5/l968 Klock 2l0/256 XPrimary Examiner-Michael Rogers Attorney-Ira Milton Jones ABSTRACT:Contaminated raw or waste water is delivered into at least one basinwhich is supported within a water-filled reservoir. The contaminatedwater in said basin is subjected to mechanical, biological and/orchemical purification, and the treated effluent is caused to overflowinto the reservoir. The basin has a conical wall of supple nonporousmaterial that yields readily to even slight movements of the water bothinternally and externally of the basin unit.

PATENTEDNUV 9 19m 3 6 1 8 7 7 3 sum 1 BF 2 lNvaNTonL E'ten Jan 11527ATT'O Y WATER PURIFICATION APPARATUS This invention is concerned withsewage disposal and waste water purification problems.

In conventional sewage disposal and waste water purification plantsthe'various basins and tanks that are an essential part of all suchplants are customarily concrete and metal structures. Accordingly alarge proportion of the cost of a water purification plant results fromthe expense involved in building and fabricating these basins and tanks.

The present invention eliminates the need for costly concrete and metalstructures to receive and hold the contaminated water while it isundergoing treatment, by floating or otherwise suspending one or morebasins formed of supple nonporous material in a body of water which maybe a natural pond or small lake, or an inexpensive ground excavation.The contaminated water is delivered into the flexible walled basin orbasins where the purification process is carried out. The sedimentcollects in the bottom of the basins, and treated clear water flows fromthe upper levels thereof into the body of water in which the basins aresuspended.

While the use of flexible walled basins suspended in water is not per senew in sewage disposal and water purification plants, as evidenced bythe Klock US Pat. No. 3,385,786 heretofore the removal of the sludgefrom the basins presented a problem which was aggravated by the flexiblenature of the basin walls. Obviously, of course, the sludge must belifted or drawn from the basins without disturbing the relatively cleartreated water in the uppermost portions of the basins, but in all priorattempts to substitute water-supported flexible walled basins for therigid structures used in more conventional water purification plants, itwas impossible to effect sludge removal without agitating and stirringup the basin contents. Due to the shape of the basins that were used inthe past and the suppleness of their walls, any substantial disturbanceeither inside or outside of a basin resulted in such violent agitationof its contents that satisfactorily complete separation of the sedimentsand/or contaminants from the water undergoing treatment was well-nighimpossible. The present invention solves the problem heretoforepresented by the use of supple-walled basins in sewage disposal andwater purification plants by so shaping the basin walls that allportions thereof converge and slope downwardly to a zone of small volumeat the bottom of the basin from which sludge can be readily removed.

The resulting absence of a large flat or substantially flat bottom wallprecludes accumulation of sludge over areas and on surfaces from whichit cannot be removed except by severe flexure of the basin walls, andinstead makes it possible to continuously draw the accumulating sludgefrom the basin by a suction pump having the mouth of its intake tubefixedly mounted in the small volume bottom portion of the basin.

Since it is important in avoiding rolling of accumulated sedirrent inthe basin or basins that their bottoms should not be displaced, it isalso an object of the invention to maintain the water in which the basinor basins are floatingly suspended at a constant level, to assure thattheir bottoms will be supported well above the bottom of the pond, lakeor reservoir.

The maintenance of a constant level of the water in the reservoir isalso advantageous in that it enables the basin to be fixedly suspendedtherein without danger of excessive strain upon its relatively thinwalls, such as would otherwise result if the water level in thereservoir dropped by any appreciable amount.

With these observations and objectives in mind, the manner in which theinvention achieves its purpose will be appreciated from the followingdescription and the accompanying drawings, which exemplify theinvention, it being understood that such changes in the precise methodof practicing the invention and in the specific apparatus disclosedherein may be made as come within the scope of the appended claims.

The accompanying drawings illustrate two complete examples of theembodiments of the invention constructed according to the best modes sofar devised for the practical application of the principles thereof, andin which:

FIG. 1 is a diagrammatic view of a reservoir-type water purificationplant embodying this invention;

FIG. 2 is a plan view of the plant seen in FIG. 1;

FIG. 3 is a diagrammatic view of another embodiment of the invention inwhich a pair of basin units are fixedly suspended in the reservoir;

FIG. 4 is a plan view of the plant shown in FIG. 3; and

FIG. 5 is a fragmentary sectional detail view taken on.the line 5-5 inFIG. 4.

Referring now to the accompanying drawings, and in particular to FIGS. 1and 2, the reference numeral 15 denotes an artificially producedreservoir which is in the form of an excavation that more or lessdefines a pit. The reservoir has walls that are substantially watertight, and it is filled with water that is substantially free ofcontaminants.

A basin 16 having walls formed of supple nonporous material ispositioned within the reservoir, and contaminated water is treatedtherein. The basin is supported in the reservoir water as by means of acircular flotation collar 17 secured to the rim at the upper edge of itssidewall 18. To. give the basin the desired suppleness and nonporousquality, its wall 18 is preferably made of a plastic material based onpolyvinyl chloride reinforced by fabric.

Outlet openings 19 are provided in the upper edge portion of the basinwall 18 at a slight distance below the flotation collar 17, throughwhich the substantially clear water that obtains in the top portion ofthe basin flows into the reservoir. To guard against the passage of anydebris that may be floating on the surface in the basin, the openings 19may be placed far enough below water level to assure that only clearwater from below the surface will be transferred to the reservoir. Inthe embodiment shown in FIGS. I and 2, the basin 16 has apurely invertedconical shape, so that its sidewall 18 converges towards the apex 20 ofthe cone, at the lowermost point of the basin.

Associated with the plant is a bridge 21 supported over the reservoir onfloats 22 that are retained in position within the reservoir by means ofanchoring wires 23.

Sewage or waste water to be treated is supplied to the basin 16 througha conduit 24 having a flexible portion 25 adjacent to the basin tominimize such movements of its sidewall as are caused by bodily motionof the basin relative to the rigid outer portion 24 of the conduit. Inthe embodiment shown, the conduit for the waste water extends into thecenter of the basin unit 16 and opens into a chamber 26 therein, inwhich chemical or biological purification of the influent is effected ina known manner. Water thus treated in the chamber 26 overflows therefrominto the basin 16, where the solids sink to the bottom. Alternatively,such water can be recycled as return sludge into the chamber 26.

When the solids or sediment gravitates towards the bottom of the basin16 it will to some extent come in contact with the inner surfaces of thebasin sidewall 18 and tend to form a gradually growing layer thereon.This layer would continue to build up in a basin having rigid walls ofsheet plate or concrete, but in the present case, the normal motion ofthe water in the basin and/or in the surrounding body of water willcontinuously impart more or less gentle undulatory movements ordeflections to the basin wall to discourage accumulation of sedimentthereon. Instead, such gentle movements will taminated water enteringthe same, that the basin is always kept full, with clear relativelyuncontaminated water flowing into the reservoir from the basin outlets19. Hence the internal and external pressures on the wall of the basinwill be substantially equal and the elevation of the basin in the bodyof water in which it is floatingly suspended will remain substantiallyfixed. Damaging strains on the thin wall of the basin is impossiblesince the internal pressure can never exceed the external pressure, andif perchance the withdrawal of sludge proceeds more rapidly than theentry of contaminated water into the basin, the suppleness of the basinwall simply permits it to adjust itself to the reduced volume of thebasin contents. This of course does not strain the basin wall nor doesit alter the elevation of the basin in the reservoir since thesuppleness of the basin wall assures the maintenance of the correctbalance between volume and buoyancy.

The supply of water in the reservoir is comprised of purified water fromthe basin 16, along with whatever quantities of fresh water from a lakeor the like are necessary to maintain a constant predetermined level inthe reservoir. An overflow outlet 32 provides for discharge of purifiedwater from the reservoir and a simple water supply valve 33 controlledby a float 34 regulates the admission of water into the reservoir tomaintain the desired water level therein.

From the foregoing description, it will be seen that the waterpurification method of this invention is characterized by the treatmentof contaminated water in the interior of a basin having highly flexiblesidewalls that converge downwardly to a localized zone at its bottom,from which zone accumulated sludge can be readily pumped; suspension ofthe basin in a water filled reservoir wherein the water level is keptconstant; and transfer of purified water to the reservoir from a clearwater zone near the top of the basin.

In the purification plant shown in FIGS. 3 and 4, the reservoir heredenoted by the reference numeral 150 comprises a ground excavation orpit 36, the sidewalls of which are lined with sheeting 37 driven downinto the ground. The bottom of the reservoir may be covered with a layer38 of asphalt if necessary to prevent undue leakage.

The waste or contaminated raw water to be purified is introduced intothe plant through a duct 39 which debouches into a dividing channel 40.At this point a grate 41 separates out solid impurities of larger size,and a sand trap 42 of large dimensions slows down the flow of theincoming water. From the trap 42 the incoming water flows through aconduit 43 that leads to a basin 48 which, like the basin 16 issuspended in the water filling the reservoir 150. The conduit 43discharges into an aeration device 44, mounted in the interior of thebasin 48 and consisting of two opposed and telescoped containers 45 and46, the former positioned concentrically within the latter. The outercontainer 46 opens downwardly, while the inner container 45 opensupwardly into the inverted outer container. The sidewalls of the twocontainers are spaced apart to form an annular interspace 47therebetween.

One or more air inlets (not shown) admit air into the inner container45.

The waste water overflowing from the top of the inner container passesdownwardly through the interspace 47 into the lower portion of the basin48 where the sludge accumulates. Treated water flows into an overflowtrough 49 from the upper portion of the basin 48. The trough 49encircles the aeration device 44, and a conduit 50 connecting with thetrough delivers the treated water into a chamber 51 containing chemicalsfor effecting flocculation in a manner known per se.

The chamber 51 is located between the basin 48 and a second basin 53which is also suspended in the reservoir 150 and provides a clarifyingreceptacle. Water from the flocculation chamber 51 is passed on to theclarifying basin 53 through a conduit 52 which opens to a centraldistributing tube 54. The tube 54 flares outwardly towards its lowerend, and the basin 53 has an overflow trough 55 which encircles the tube54 and is communicated through a duct 56 with the reservoir 150.

Accordingly, in this embodiment of the invention, the contaminated wateris subjected to two purification steps, viz separate biological andchemical purification steps, and it is to a substantial degree free fromharmful impurities by the time it is discharged into the reservoir 150.

The basins 48 and 53, like the basin 16, may be provided with flotationcollars at their tops, or they may be attached to the sidewalls of thereservoir as shown, or supported in part from the reservoir sidewallsand from footbridges 57 which extend across the reservoir.

Also, like the basin 16, the basins 48 and 53 have converging sidewallsmade of thin flexible material such as fabric reinforced polyvinylchloride, having a thickness of between 0.6 and 0.9 millimeters. In thiscase, however, the walls of the basins are comprised of flat panels 58shaped to give the basin the appearance of a truncated but invertedpyramid.

The level of the water in the basins 48 and 53 is maintained onlyslightly above that of the water in the reservoir I50. Not only doesthis substantially equalize the internal and external pressure on thebasin walls, but it also enables self-drainage of the water seriallythrough the basins 48 and 53 into the overflow 55in basin 53.

Due to their extreme thinness, the inclined walls of the basins can havea gentle vibratory movement imparted thereto in a simple manner, e.g.,by means of compressed air introduced into the water contained in thesurrounding reservoir and alongside the basins. This assures that sludgethat may have settled on the basin walls will be gently dislodgedtherefrom to migrate toward the bottoms of the basins.

The sludge collected in the small volume bottom zones of the basins 48and 53 can be easily pumped therefrom through drawoif tubes 60 that arearranged to discharge into a sludge trough 61 having outlets into eachof a pair of mineralizing basins 62. The sludge can thereafter betreated in a conventional manner on sludge drying beds or the like.

The outer basin or reservoir 150, of course, has an overflow 63 to whicha discharge conduit 64 is connected.

The plant may also be provided with a superstructure 65 that encloses itto avoid formation of ice in cold climates.

If any impurities should be detected in the outer basin or reservoir150, due to discharge thereinto of water from the outlet of the basin53, the water from the reservoir can be returned to the intake of theplant for reprocessing, or to one of the basins. Preferably suchrecirculation is carried out at night only, when the volume of wastewater requiring treatment is low.

The method of water purification carried out in the plant shown in FIGS.3-5 is similar to that described in connection with the plant disclosedin FIGS. 1 and 2, except that treatment is effected in a way thatutilizes two plastic-walled basins suspended in a water-filledartificial reservoir.

While more or less specific embodiments of the invention have been shownand described, those skilled in the art will appreciate that theinvention can be embodied in forms other than as herein disclosed forpurposes of illustration.

The invention is defined by the following claims:

Iclaim:

l. A plant for purification of water contaminated by sewerage or thelike, characterized by:

A. means defining a reservoir that contains water substantially freefrom contaminants;

B. a basin in which contaminated water is to be treated,

B. having sidewalls of a nonporous material which is supple enough to beyieldably moved by movements of water in contact therewith, to therebypromote downward migration along the inner surfaces of said walls ofsludge that tends to settle on them, and

B. having its sidewalls converging toward an apexlike localized zone ofsmall volume at the bottom of the basin, to facilitate the removal ofaccumulated sludge from the bottom of the basin;

C. means for introducing substantially untreated water into the basin ata level which is spaced below that of water in the reservoir and spacedabove the bottom of the basin;

D. means suspending the basin in the reservoir with the rim of the basinabove reservoir water level but with the major portion of the basinsidewalls below said level and thus subject to movement by motionofwater in the reservoir and in the basin;

E. means for maintaining substantially uncontaminated water in thereservoir to a depth which is equal to at least a major portion of theheight of the basin, the last mentioned means comprising outlet means inthe basin at a level above said level at which untreated water isintroduced thereinto, for transferring to the reservoir treated waterfrom a high level zone in the basin; and

F. a sludge withdrawal duct having an inlet in the basin at a level nearthe bottom thereof and which is connectable with a suction source toprovide for withdrawing accumulated sludge from the bottom of the basin.

level below that of water in the reservoir, to prevent floating materialin the basin from passing into the reservoir.

3. The water purification plant of claim 1, wherein said means formaintaining substantially uncontaminated water in the reservoir furthercomprises: a fresh water supply valve for the reservoir; and a floatactuator for said valve that is responsive to the level of water in thereservoir.

2. The water purification plant of claim 1, wherein said outlet means inthe basin comprises apertures in its sidewalls at a level below that ofwater in the reservoir, to prevent floating material in the basin frompassing into the reservoir.
 3. The water purification plant of claim 1,wherein said means for maintaining substantially uncontaminated water inthe reservoir further comprises: a fresh water supply valve for thereservoir; and a float actuator for said valve that is responsive to thelevel of water in the reservoir.